Comparison of greenhouse gas emissions from sheep measured using both respiration and portable accumulation chambers

Methane (CH4) is a potent gas produced by ruminants, and new measurement techniques are required to generate large datasets suitable for genetic analysis. One such technique are portable accumulation chambers (PAC), a short-term sampling method. The objectives of the current study were to explore the relationship between CH4 and carbon dioxide (CO2) output measured using both PAC and respiration chambers (RC) in growing lambs, and separately investigate the relationship among CH4, CO2 and measured ad libitum DM intake (DMI). Methane, CO2 and DMI were measured on 30 Suffolk and 30 Texel ewe lambs (age 253 ± 12 days) using the RC and PAC sequentially. The experiment was conducted over a 14-day period, with DMI measured from days 1 to 14; measurements in RC were conducted from days 10 to 12, while measurements in PAC were taken twice, the day immediately prior to the lambs entering the RC (day 9; PAC Pre-RC) and on the day lambs exited the RC (day 13; PAC Post-RC). Greater CH4 and CO2 output was measured in the RC than in the PAC (P < 0.01); similarly mean CH4 yield was greater when measured in the RC (15.39 ± 0.452 g CH4/kg DMI) compared to PAC (8.01 ± 0.767 g CH4/kg DMI). A moderate correlation of 0.37 was found between CH4 output measured in PAC Pre-RC and the RC, the corresponding regression coefficient of CH4 output measured in the RC regressed on CH4 output measured in PAC Pre-RC was close to unity (0.74; SE 0.224). The variance of CH4 and CO2 output within the measurement technique did not differ from each other (P > 0.05). Moderate to strong correlations were found between CH4 and CO2 per kg of live weight and CH4 and CO2 yield. Results from this study highlight the suitability of PAC as a ranking tool to rank animals based on their gaseous output when compared to the RC. However, repeated measurements separated by several days may be beneficial if precise rankings are required. Given the close to unity regression coefficient of CH4 output measured in the RC regressed on CH4 output measured in PAC Pre-RC suggests that PAC could also be potentially used to estimate absolute CH4 output; however, further research is required to substantiate this claim. When DMI is unknown, CH4 and CO2 per kg of live weight are a suitable alternative to the measurement of CH4 and CO2 yield.

Deneddylation of ribosomal proteins promotes synergy between MLN4924 and chemotherapy to elicit complete therapeutic responses

The neddylation inhibitor MLN4924/Pevonedistat is in clinical trials for multiple cancers. Efficacy is generally attributed to cullin RING ligase (CRL) inhibition, but the contribution of non-CRL targets is unknown. Here, CRISPR screens map MLN4924-monotherapy sensitivity in retinoblastoma to a classic DNA damage-induced p53/E2F3/BAX-dependent death effector network, which synergizes with Nutlin3a or Navitoclax. In monotherapy-resistant cells, MLN4924 plus standard-of-care topotecan overcomes resistance, but reduces DNA damage, instead harnessing ribosomal protein nucleolar-expulsion to engage an RPL11/p21/MYCN/E2F3/p53/BAX synergy network that exhibits extensive cross-regulation. Strikingly, unneddylatable RPL11 substitutes for MLN4924 to perturb nucleolar function and enhance topotecan efficacy. Orthotopic tumors exhibit complete responses while preserving visual function. Moreover, MLN4924 plus melphalan deploy this DNA damage-independent strategy to synergistically kill multiple myeloma cells. Thus, MLN4924 synergizes with standard-of-care drugs to unlock a nucleolar death effector network across cancer types implying broad therapeutic relevance.

Binary pan-cancer classes with distinct vulnerabilities defined by pro- or anti-cancer YAP/TEAD activity

Cancer heterogeneity impacts therapeutic response, driving efforts to discover over-arching rules that supersede variability. Here, we define pan-cancer binary classes based on distinct expression of YAP and YAP-responsive adhesion regulators. Combining informatics with in vivo and in vitro gain- and loss-of-function studies across multiple murine and human tumor types, we show that opposite pro- or anti-cancer YAP activity functionally defines binary YAP^on or YAP^off cancer classes that express or silence YAP, respectively. YAP^off solid cancers are neural/neuroendocrine and frequently RB1^-/-, such as retinoblastoma, small cell lung cancer, and neuroendocrine prostate cancer. YAP silencing is intrinsic to the cell of origin, or acquired with lineage switching and drug resistance. The binary cancer groups exhibit distinct YAP-dependent adhesive behavior and pharmaceutical vulnerabilities, underscoring clinical relevance. Mechanistically, distinct YAP/TEAD enhancers in YAP^off or YAP^on cancers deploy anti-cancer integrin or pro-cancer proliferative programs, respectively. YAP is thus pivotal across cancer, but in opposite ways, with therapeutic implications.

Sampling strategy for bacteriological diagnosis of intrathoracic tuberculosis

BACKGROUND

Pulmonary tuberculosis (TB) is the most frequent site of TB and the one leading its spread worldwide. Multiple specimens are commonly collected for TB diagnosis including those requiring invasive procedures. This study aimed to review the sampling strategy for the microbiological diagnosis of pulmonary TB.

METHODS

A retrospective analysis of collected samples from September 1st 2014 to May 1st 2016 in the Bacteriology laboratory of Pitié-Salpêtrière Hospital (Paris, France) was performed. All the samples collected in patients aged over 18 years for the bacteriological diagnosis of pulmonary TB were included.

RESULTS

A total of 6267 samples were collected in 2187 patients. One hundred and twenty-six patients (6%) had a culture confirmed pulmonary TB. Among them, multiple sputum collections were sufficient for TB diagnosis in 63.5%, gastric lavages permitted to avoid bronchoscopy in only 7.1%, and bronchoscopy was necessary in 29.4%. The culture positivity of sputa (8.6%) was higher than that of bronchial aspirations (3.1%), bronchiolo-alveolar lavages (BAL) (2.3%) or gastric lavages (4.8%) (P<0.001). From its 70.0% theoretical PPV value, the 46.1% selection in bronchial aspirations allocated to molecular test increased PPV up to 88.9%.

CONCLUSIONS

Based on our data, we suggest to collect sputum consistently. If smear negative a bronchoscopy should be performed and molecular diagnosis be performed on a subset of bronchial aspirations based on expertise of the bronchoscopist.

Comparison of polysaccharide glycoconjugates as candidate vaccines to combat Clostridiodes (Clostridium) difficile

Two known Clostridiodes (Clostridium) difficile surface antigens, a lipoteichoic acid (LTA) and a polysaccharide (PS-II) were isolated and purified in order to prepare glycoconjugate vaccines to the carrier protein human serum albumin utilising a reductive amination strategy. Mice and rabbits were immunized with a prime and two boost strategy and the resulting sera were examined for their ability to recognise the purified homologous antigens and subsequently killed whole cells of C. difficile strains and other Clostridia species. Immunisation derived antisera from rabbits and mice, recognised all strains of C. difficile vegetative cells examined, with generally similar titers from animals that received the LTA or the PS-II conjugates. Sera raised to the LTA conjugates were able to recognise other Clostridia species C. butyricum, C. bifermentans and C. subterminale whereas sera raised to the PS-II conjugates were not. These LTA and PS-II sera recognised live cells in an immunofluorescence assay and were also able to recognise the spore form of the bacterium. This study has confirmed that the LTA and PS-II polysaccharides are both highly conserved surface polymers of C. difficile that are easily accessible to the immune system and as such may have potential as vaccine antigens or as targets for therapeutics to combat C. difficile infection.

Multidisciplinary advisory teams to manage multidrug-resistant tuberculosis: the example of the French Consilium

SETTING: The World Health Organization (WHO) recommends that multidrug-resistant tuberculosis (MDR-TB) treatment should be managed in collaboration with multidisciplinary advisory committees (consilia). A formal national Consilium has been established in France since 2005 to provide a centralised advisory service for clinicians managing MDR-TB and extensively drug-resistant (XDR-TB) cases.OBJECTIVE: Review the activity of the French TB Consilium since its establishment.DESIGN: Retrospective description and analysis of the activity of the French TB Consilium.RESULTS: Between 2005 and 2016, 786 TB cases or contacts of TB cases were presented at the French TB Consilium, including respectively 42% and 79% of all the MDR-TB and XDR-TB cases notified in France during this period. Treatment regimens including bedaquiline and/or delamanid were recommended for 42% of the cases presented at the French TB Consilium since 2009. Patients were more likely to be presented at the French TB Consilium if they were born in the WHO Europe Region, had XDR-TB, were diagnosed in the Paris region, or had resistance to additional drugs than those defining XDR-TB.CONCLUSION: The French TB Consilium helped supervise appropriate management of MDR/XDR-TB cases and facilitated implementation of new drugs for MDR/XDR-TB treatment.

[Molecular diagnosis of tuberculosis]

Tuberculosis is caused by the M. tuberculosis complex. Its slow growth delays the bacteriological diagnosis based on phenotypic tests. Molecular biology has significantly reduced this delay, notably thanks to the deployment of the Xpert® MTB/RIF test (Cepheid), which detects the M. tuberculosis complex and rifampicin resistance in 2hours. Other tests detecting isoniazid and second-line antituberculous drugs resistance have been developed. However, the performances of molecular tests are significantly reduced if the acid-fast bacilli microscopy screening is negative. It is therefore crucial to limit their indication to strong clinical suspicions. Resistance detection tests only explore certain characterized positions; however, not all drug-resistance mutations are known. Moreover, the performances vary for different antituberculous drugs. The advent of genomic sequencing is promising. Its integration into routine workflow still needs to be evaluated and the data analysis remains to be standardized. The rise of molecular biology techniques has revolutionized the diagnosis of tuberculosis and drug resistance. However, they remain screening tests; results still have to be confirmed by phenotypic reference methods.

[Cor pulmonale]

Cor pulmonale is a disease of the heart characterised by dilatation of the right ventricle and paradoxical movement of the interventricular septum. The diagnosis depends on echocardiography even if pulmonary artery catheterisation suggests it. It is secondary to pulmonary disease or a disorder of the pulmonary circulation. These two mechanisms, which are often connected, involve pulmonary hypertension as the origin of a systolic and diastolic overload of the right ventricle, which then leads to the alterations of its structure and performance. Acute cor pulmonale is usually secondary to an acute respiratory distress syndrome or to a pulmonary embolism but it can also be seen in primary lactic acidosis, a vaso-occlusive crisis in a patient with sickle cell anaemia, severe acute asthma, and entry of air or injected crushed tablets into the circulation. Chronic cor pulmonale is the terminal stage of pulmonary hypertension. Clinically these patients are dyspnoeic with signs of chronic right heart failure. They should have an echocardiogram confirming the cardiac involvement. Certain precipitating factors, such as infection of any origin, have been reported, leading to acute on chronic cor pulmonale that has a particularly high mortality.

Preclinical studies reveal MLN4924 is a promising new retinoblastoma therapy

RB1 loss (RB1 null ) or MYCN amplification (MYCN amp ) in fetal human retina causes retinoblastoma. SKP2 loss kills RB1 null cells, but small molecule SKP2 inhibitors remain unexplored therapeutically. Whether SKP2 is synthetic lethal in MYCN amp retinoblastoma is unclear. SKP2 is the substrate recognition component of two Cullin-RING Ligase complexes (CRL1SKP2/SCFSKP2, and CRL4SKP2), a family of multiprotein E3 ubiquitin ligases. NEDD8 activating enzyme (NAE) is required for Cullin neddylation and thus CRL activation. Here, we show that the NAE inhibitor, Pevonedistat (MLN4924), potently inhibits RB1 null and MYCN amp tumors. Intravitreal MLN4924 suppressed multiple human xenografts with EC80s from 20 ng to 3.5 μg. Maximum tolerated dose (MTD) was 10-30 μg, highlighting a favorable therapeutic window. Inhibition of Cullin neddylation was similar in all cases, but cellular effects ranged from G1 arrest with apoptosis to G2/M arrest with endoreplication. However, even in less sensitive lines (EC50 ≈ 1 μM), prolonged exposure was lethal or induced persistent cytostasis. Mechanistically, depleting any single Cullin did not fully recapitulate drug phenotypes, but sensitivity to SKP2 loss correlated with that of drug. Thus, intravitreal MLN4924 is a promising new retinoblastoma therapy, mimicking the cancer-specific lethality of eliminating SKP2 complexes.

Risk factors for extensive drug resistance in multidrug-resistant tuberculosis cases: a case-case study

SETTINGS

Identification of extensively drug-resistant tuberculosis (XDR-TB) may be delayed because of the lack of availability of molecular testing for second-line drugs (SLDs). Early suspicion of XDR-TB is therefore necessary to avoid developing further drug resistance.

OBJECTIVE

To identify the characteristics associated with XDR-TB among multidrug-resistant TB (MDR-TB) cases before the availability of second-line drug susceptibility testing (DST) results.

METHODS

All MDR-TB cases with available second-line DST results recorded in France from 1998 to 2013 were classified as simple MDR-TB (no resistance to fluoroquinolones [FQs] or second-line injectable drugs [SLIDs]), pre-XDR-TB (resistance to FQs or SLIDs) and XDR-TB cases (resistance to both).

RESULTS

A total of 833 MDR-TB cases were analysed, including 168 (20%) pre-XDR and 62 (7%) XDR-TB cases. A previous history of treatment was acknowledged among 41% of the cases; 12% were human immunodeficiency virus-positive. Characteristics independently associated with XDR-TB were foreign birth (OR 9.5), previous anti-tuberculosis treatment (OR 2.6), smear positivity (OR 4.5) and ethambutol (EMB) resistance (OR 9.1). Characteristics independently associated with pre-XDR-TB compared to simple MDR-TB cases were male sex (OR 1.6), birth in Europe (OR 2.6) and EMB resistance (OR 1.9).

CONCLUSION

The presence of clinical or bacteriological characteristics associated with XDR-TB should lead to rapid molecular testing for resistance to SLDs before starting tailored treatment.

Re-emergence of Corynebacterium diphtheriae

BACKGROUND

Diphtheria is re-emerging in Europe. A total of 36 cases were reported in Europe in 2015 versus 53 cases between 2000 and 2009.

PATIENTS

We report two cases of Corynebacterium diphtheriae infection in a French hospital in 2016: a cutaneous infection with negative toxin testing in a French traveller, and a respiratory diphtheria carriage with positive toxin testing in an Afghan refugee diagnosed with pulmonary tuberculosis. The vaccination history of the Afghan patient could not be retrieved.

Interpreting carbapenem susceptibility testing results for Pseudomonas aeruginosa

OBJECTIVES

Carbapenems are among the most powerful antipseudomonal agents. Limited data is available on drug susceptibility testing by routine methods (disc diffusion and Etest) for meropenem and doripenem. We aimed to compare the in vitro activity of imipenem, meropenem, and doripenem against Pseudomonas aeruginosa.

METHODS

A total of 311 P. aeruginosa strains isolated from respiratory specimens in 170 patients who developed ventilator-associated pneumonia in two intensive care units were collected over a period of 31 months. The susceptibility of these isolates to imipenem, meropenem, and doripenem were determined by Etest and disc diffusion method.

RESULTS

Considering either all isolates or only the first isolates recovered per patient (311 and 170 respectively), the susceptibility rate for doripenem was higher than that for meropenem and imipenem. When MICs determined by Etest were converted into interpretative categories (S, I, R) using French (CA-SFM) guidelines, a poor correlation was observed for meropenem and doripenem. The percentages of correlation with the disc diffusion method were 90.6% and 89.7% for imipenem, 80.5% and 82.6% for meropenem, and 80.5% and 73.3% for doripenem, for the first isolates and all isolates, respectively. The rate of minor errors was as high as 17.7% and 16.1% for meropenem and 17.7% and 25.7% for doripenem for the first isolates and all isolates, respectively.

CONCLUSION

The accuracy of disc diffusion using CA-SFM guidelines appears unsatisfactory for all three carbapenems justifying guideline update for P. aeruginosa and carbapenems.

Investigation of pre-XDR Beijing Mycobacterium tuberculosis transmission to a healthcare worker in France, 2016

A case of occupational contamination of a healthcare worker by a pre-extensively drug-resistant (pre-XDR) Beijing strain of Mycobacterium tuberculosis at the University Hospital of Montpellier, France is reported. The index case was identified using genetic fingerprinting of isolates. This report underscores the risk of healthcare-associated contamination by pre-XDR tuberculosis (TB) in low-incidence countries and the importance of molecular tools for TB care. It also calls for increased vigilance in the management of multi-drug-resistant/XDR TB patients.

Properties of STAT1 and IRF1 enhancers and the influence of SNPs

BACKGROUND

STAT1 and IRF1 collaborate to induce interferon-γ (IFNγ) stimulated genes (ISGs), but the extent to which they act alone or together is unclear. The effect of single nucleotide polymorphisms (SNPs) on in vivo binding is also largely unknown.

RESULTS

We show that IRF1 binds at proximal or distant ISG sites twice as often as STAT1, increasing to sixfold at the MHC class I locus. STAT1 almost always bound with IRF1, while most IRF1 binding events were isolated. Dual binding sites at remote or proximal enhancers distinguished ISGs that were responsive to IFNγ versus cell-specific resistant ISGs, which showed fewer and mainly single binding events. Surprisingly, inducibility in one cell type predicted ISG-responsiveness in other cells. Several dbSNPs overlapped with STAT1 and IRF1 binding motifs, and we developed methodology to rapidly assess their effects. We show that in silico prediction of SNP effects accurately reflects altered binding both in vitro and in vivo.

CONCLUSIONS

These data reveal broad cooperation between STAT1 and IRF1, explain cell type specific differences in ISG-responsiveness, and identify genetic variants that may participate in the pathogenesis of immune disorders.

Anderson Mobility Gap Probed by Dynamic Coherent Backscattering

We use dynamic coherent backscattering to study one of the Anderson mobility gaps in the vibrational spectrum of strongly disordered three-dimensional mesoglasses. Comparison of experimental results with the self-consistent theory of localization allows us to estimate the localization (correlation) length as a function of frequency in a wide spectral range covering bands of diffuse transport and a mobility gap delimited by two mobility edges. The results are corroborated by transmission measurements on one of our samples.

Peptides derived from the dependence receptor ALK are proapoptotic for ALK-positive tumors

ALK is a receptor tyrosine kinase with an oncogenic role in various types of human malignancies. Despite constitutive activation of the kinase through gene alterations, such as chromosomal translocation, gene amplification or mutation, treatments with kinase inhibitors invariably lead to the development of resistance. Aiming to develop new tools for ALK targeting, we took advantage of our previous demonstration identifying ALK as a dependence receptor, implying that in the absence of ligand the kinase-inactive ALK triggers or enhances apoptosis. Here, we synthesized peptides mimicking the proapoptotic domain of ALK and investigated their biological effects on tumor cells. We found that an ALK-derived peptide of 36 amino acids (P36) was cytotoxic for ALK-positive anaplastic large-cell lymphoma and neuroblastoma cell lines. In contrast, ALK-negative tumor cells and normal peripheral blood mononuclear cells were insensitive to P36. The cytotoxic effect was due to caspase-dependent apoptosis and required N-myristoylation of the peptide. Two P36-derived shorter peptides as well as a cyclic peptide also induced apoptosis. Surface plasmon resonance and mass spectrometry analysis of P36-interacting proteins from two responsive cell lines, Cost lymphoma and SH-SY5Y neuroblastoma, uncovered partners that could involve p53-dependent signaling and pre-mRNA splicing. Furthermore, siRNA-mediated knockdown of p53 rescued these cells from P36-induced apoptosis. Finally, we observed that a treatment combining P36 with the ALK-specific inhibitor crizotinib resulted in additive cytotoxicity. Therefore, ALK-derived peptides could represent a novel targeted therapy for ALK-positive tumors.

Recurrent scattering and memory effect at the Anderson localization transition

We report on ultrasonic measurements of the propagation operator in a strongly scattering mesoglass. The backscattered field is shown to display a deterministic spatial coherence due to a remarkably large memory effect induced by long recurrent trajectories. Investigation of the recurrent scattering contribution directly yields the probability for a wave to come back close to its starting spot. The decay of this quantity with time is shown to change dramatically near the Anderson localization transition. The singular value decomposition of the propagation operator reveals the dominance of very intense recurrent scattering paths near the mobility edge.

Comparison between experimental and 2-D numerical studies of multiple scattering in Inconel600 by means of array probes

Ultrasonic non-destructive testing of polycrystalline structures can be disturbed by scattering at grain boundaries. Understanding and modeling this so-called "structural noise" is crucial for characterization as well as detection purposes. Structural noise can be considered as a fingerprint of the material under investigation, since it contains information about its microstructure. The interpretation of experimental data necessitates an accurate comprehension of complex phenomena that occur in multiple scattering media and thus robust scattering models. In particular, numerical models can offer the opportunity to realize parametrical studies on controlled microstructures. However, the ability of the model to simulate wave propagation in complex media must be validated. In that perspective, the main objective of the present work is to evaluate the ability of the finite-element code ATHENA 2D to reproduce typical features of multiple wave scattering in the context of ultrasonic non-destructive evaluation, with an array of sources and receivers. Experiments were carried out with a 64-element array, around 2 MHz. The sample was a mock-up of Inconel600 exhibiting a coarse grain structure with a known grain size distribution. The numerical model of this microstructure is based on Voronoi diagrams. Two physical parameters were used to compare numerical and experimental data: the coherent backscattering peak, and the singular value distribution of the array response matrix. Though the simulations are 2-D, a good agreement was found between simulated and experimental data.

Transformation optics and subwavelength control of light

Our intuitive understanding of light has its foundation in the ray approximation and is intimately connected with our vision. As far as our eyes are concerned, light behaves like a stream of particles. We look inside the wavelength and study the properties of plasmonic structures with dimensions of just a few nanometers, where at a tenth or even a hundredth of the wavelength of visible light the ray picture fails. We review the concept of transformation optics that manipulates electric and magnetic field lines, rather than rays; can provide an equally intuitive understanding of subwavelength phenomena; and at the same time can be an exact description at the level of Maxwell's equations.

Long-term control of vancomycin-resistant Enterococcus faecium at the scale of a large multihospital institution: a seven-year experience

Binary file ES_Abstracts_Final_ECDC.txt matches

Long-term control of vancomycin-resistant Enterococcus faecium at the scale of a large multihospital institution: a seven-year experience

Repeated outbreaks of vancomycin-resistant Enterococcus faecium (VRE) occurred between 2004 and 2010 in Assistance Publique--Hôpitaux de Paris (AP-HP), a 23,000-bed multi-hospital institution. From August 2004 to December 2005, the French guidelines for preventing cross-transmission of multiresistant bacteria were applied. Because the number of VRE cases continued to increase, an institutional control programme was implemented from January 2006 onwards: it foresees stopping transfer of VRE and contact patients, separating VRE and contact patients in distinct cohorts, intervention of a central infection control team to support local teams, and quick application of measures as soon as first VRE cases are identified. Between August 2004 and December 2010, 45 VRE outbreaks occurred in 21 of the 38 AP-HP hospitals, comprising 533 cases. Time series analysis showed that the mean number of cases increased by 0.8 cases per month (95% confidence interval (CI): 0.3 to 1.3, p=0.001) before, and decreased by 0.7 cases per month after implementation of the programme (95% CI: -0.9 to -0.5, p<0.001), resulting in a significant trend change of -1.5 cases per month (95% CI: -2.1 to -0.9, p<0.001). The number of cases per outbreak was significantly lower after implementation of the programme. A sustained and coordinated strategy can control emerging bacteria at the level of a large regional multihospital institution.

Exploiting the time-reversal operator for adaptive optics, selective focusing, and scattering pattern analysis

We report on the experimental measurement of the backscattering matrix of a weakly scattering medium in optics, composed of a few dispersed gold nanobeads. The decomposition of the time-reversal operator is applied to this matrix and we demonstrate selective and efficient focusing on individual scatterers, even through an aberrating layer. Moreover, we show that this approach provides the decomposition of the scattering pattern of a single nanoparticle. These results open important perspectives for optical imaging, characterization, and selective excitation of nanoparticles.

Infections in the operated spine: update on risk management and therapeutic strategies

Among the possible risks of spine surgery, surgical site infection (SSI) is far from negligible. Incidence is higher than in other locomotor system procedures, with more severe local and general impact. Certain broad guidelines can be formulated. The risk of SSI should be taken into account in the choice of treatment options discussed with the patient. Antibiotic prophylaxis, surgical prevention of iatrogenic infection and an SSI surveillance protocol should be implemented. SSI should be suspected in case of any abnormality in postoperative course, and biological and imaging (MRI or CT) measures should be taken. Local sampling for bacteriological identification is mandatory. Treatment strategy should ideally be discussed in a multidisciplinary coordination meeting, and adapted in the light of local bacterial ecology and resistance data. The information provided to the patient should be transparent and adapted to the patient's individual context.

LEVEL OF EVIDENCE

Level V.

[Histopathological study of Mycobacterium marinum infection]

INTRODUCTION

Skin infection by Mycobacterium marinum induces the classic granuloma of aquariums and swimming pools. The histopathological signs have been described primarily in small series of typical cases, generally with no bacteriological evidence. In a national survey of proven infection with M. marinum detailed data was collected for 63 patients. The aim of this new study was to describe microscopic signs of the infection based upon biopsies taken from these patients.

PATIENTS AND METHODS

Unstained slides from 32 biopsies of the skin (n=24) or synovial biopsies (n=8) were prepared; they originated from 27 patients. They were examined after standard staining and after Ziehl-Neelsen staining, without knowledge of the clinical data.

RESULTS

All biopsies were taken from the upper limb of 18 men and nine women of mean age 48 years. Tubercular granulomas were observed in only 60% of cases. The largest and most numerous were seen in the synovial samples. Due to their palisade appearance, they were occasionally impossible to distinguish from rheumatoid nodules. In 20% of cases, neutrophil collections were seen without granulomas and in remaining 20% of cases, relatively non-specific infiltrate was observed. Epidermal changes consisted in psoriasiform or pseudocarcinomatous hyperplasia, particularly at the edges of ulcerated areas; invasion of the dermo-epidermal junction was seen in five cases. Follicular necrosis was observed in four cases with lymphoplasmacytic infiltrates remote from the granulomas being seen in 22 biopsies. Ziehl-Neelsen staining revealed no bacilli.

DISCUSSION

The originality of this series consists of bacteriological proof of M. marinum infection and the absence of biopsy selection based on clinical criteria. It shows that the typical granulomas are in fact present in less than two third of cases, and that these may be confused with rheumatoid nodules. The chief characteristic of these lesions is the very low concentration of microorganisms present, in contrast with other forms of mycobacterium, making them difficult to see; routine confirmation cannot thus be expected from specific staining procedures. In one case out of five, the infiltrate suggested no infectious origin, although deep skin biopsies and synovial biopsies provided more information. For all forms of necrotic granuloma, whether or not accompanied by collections of neutrophils, a culture should be carried out in a specific medium, even in the absence of microscopic evidence of bacilli.